Igniters for gas turbine engines



United States Patent [72] Inventors Cyril Charles Jones Stanmore;William Roger Vanryne, Bourne End, England [2i] Appl. No. 750,287

[22] Filed Aug. 5,1968

[45] Patented Nov. 24, 1970 [73] Assignee Rotax Limited London, Englanda British company [32] Priority Aug. 4, 1967 [33] Great Britain [54]IGNITERS FOR GAS TURBINE ENGINES 7 Claims, 3 Drawing Figs.

US. Cl 431/258 F23q 7/06 43 H258, 196

[56] References Cited UNITED STATES PATENTS 3,242,967 3/1966 Schmitt 43H258 3,307,610 3/1967 Sunday 431/258 Primary Examiner-Edward G. FavorsArlorney- Holman, Glascock, Downing & Seebold ABSTRACT: An igniter forigniting air/fuel mixtures in combustion chambers and comprising asleeve member in which is mounted a target against which a jet of fuelimpinges thereby to atomize the fuel, the atomized fuel being mixed withan annular air stream flowing in the same direction as the jet of fueland the air/fuel mixture being ignited by an electric heating elementdisposed internally of the airstream and upstream of the target plate.

Patented Nov. 24, 1970 3,542,501

Sheet 2 of 2 M Maw 46 ATTORNEY IGNITERS FOR GAS TURBINE ENGINES Thisinvention relates to igniters for igniting air/fuel mixtures incombination chambers and has for its object to provide such an igniterin a simple and convenient form.

An igniter in accordance with the invention comprises in combination, anorifice through which liquidfuel can be directed under pressure. atarget upon which the jet of fuel leaving the orifice impinges, thetarget being shaped so as to atomize and direct the fuel radiallyrelativethe the jet, means for producing an axially moving annularairstream into which the atomized fuel is directed. and means forigniting the air/fuel mixture to produce a flame which can be used tocause ignition ofthe air/fuel mixture in the combustion chamber.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of an igniter inaccordance with the invention;

FIG. 2 shows a modification of part of the igniter of HO. 1;

and

FIG. 3 shows how the igniter is mounted in the combustion chamber ofagas turbine engine.

As shown in FIG. 1 of the drawings the igniter comprises a cylindricalbody part having a stepped external periphery. The narrower portion ofthe body part is provided adjacent the steps with a screw thread wherebyit can be engaged within a threaded mounting boss and when so mountedthe narrower end of the body part projects into the combustion charriberin which it is desired to ignite an air/fuel mixture. As shown in FIG.3, the mounting boss 11 is carried by an external casing 12 of thecombustion chamber whose wall is indicated at 13.

Formed in the body part 10 is a stepped bore 14 the wider portion ofwhich lies within the wider portion ofthe body part. The narrowerportion of the bore terminates in a restricted outlet 15 and throughwhich the flame leaving the igniter enters the combustion chamber.Furthermore, formed in the narrow portion of the body part intermediatethe screw threaded portion and the end thereof is a ring of air inletapertures 16 which extends into the narrower portion of the bore 14-.

Extending with in the narrower portion of the bore 14 is a sleeve member17 having an outwardly directed flange 18 which is disposed within thewider portion of the bore. The sleeve member extends to a point adjacentthe outlet 15 and its outer periphery is less than that of the narrowerportion of the bore thereby defining an annular chamber 19 to which airis supplied through the apertures 16. The end of the chamber 19 adjacentthe narrower end of the bore is closed by an inter nal flange formed onthe wall of the bore 14 and this acts to locate the sleeve member withinthe narrower portion of the bore. The diameter of the flange 18 is thesame as that of the wider portion of the bore so that the sleeve memberis located at both ends.

Formed in the wall of the sleeve member is a first row of apertures 20these being positioned near the flange l8 and a second row of apertures2i which are positioned substantially midway between the ends of thesleeve member. The apertures 20 are larger in size than the apertures21.

Located within the sleeve member 17 at a position adjacent but on thesame side of the row of apertures 21 as the row of apertures 20 is atarget 22. The target 22 is mounted by means of a stout wire support 23and is of generally conical form with its base surface substantiallyflat and normal to the longitudinal axis of the igniter. The basesurface defines a target surface as will be described. The sleeve membertogether with its associated flange is formed from metal and extendinginto the sleeve member is an annular heating element support 24 hav-,

ing a flange positioned within the wider portion of the bore 14. Thesupport 24 is provided with a lining 24a formed from a ceramic materialand its annular end surface is of concave form and supports a coiledelectric heating element 25. The outer diameter of the support 24 isslightly smaller than the internal diameter of the sleeve member 17 sothat an annular clearanceis provided communicating with the apertures20. The connections for the heating element are led through elongatedpassages respectively formed in the lining 2.4a and are connectedrespectively to the body part and an electrical connecter as willbedescribed.

The electrical connecter comprises an annular ring 26 formed from metaland which is provided with an integral tag 27 which extends through anaperture formed in a first heatresistant insulating washer 28 which ispositioned intermediate the flange of the support 24 and a pressure pad29 slidable in the wider portion of the bore 14. Also provided are apair of thinner heat-resistant insulating washers 30 which arepositioned on opposite sides of the ring 26 and which are mounted withinthe washer '28. Trapped between the pressure pad 2? and the adjacentwasher 30 is one of the connections of the heating element and the otherconnection is trapped between the ring 26 and the other washer. Thepressure pad 29 is formed from metal and is held in position by anexternally threaded nut 31 which is engaged with a complementarilythreaded portion of the wider portion of the bore M.

Formed integrally with the pressure pad 29 is a stem 32 which at itsfree end is formed as a fuel inlet. The stem is hollow and is providedwith a stepped bore 33. Adjacent the step in the bore is an orificeplate 34 in which is formed a centrally disposed orifice and upstream ofthe orifice plate is a filter pad 35 the pad being secured to aretaining nut 36 which acts to retain the orifice plate in position.

In use, liquid fuel under pressure is supplied to the inlet and ajetoffuel emerges from the orifice of the orifice plate 34 and strikes thetarget 22. Upon striking the plate the fuel is atomized and directedradially and is mixed with air leaving the annular clearance between thesupport 24 and the sleeve member 17. This air entering through apertures20. Some droplets of fuel impinge upon the heating element and are ig'nited thereby and a flame emerges from the outlet 15 which is used toignite the air/fuel mixture in the combustion chamber. The air enteringthrough the apertures 21 acts to stabilize the flame.

In the alternative arrangement of HG. 2 the apertures 21 are omitted butthe flame is stabilized by rods 40 extending inwardly from the sleevemember 17, and positioned downstream of the target face.

In order to prevent blow back of fuel a nonreturn valve 41 may beprovided upstream of the fuel inlet and if desired and depending uponthe nature of the fuel, a fuel preheater 42 may be provided upstream ofthe valve 41. Reference numeral 43 indicates a pump for supplying fuelunder pressure and reference numeral 44 a source of electric supply forthe heat ing element 25v ln order to prevent a stagnant zone occuringwithin the bore in the lining 24a three equiangularly spaced passages 50(only one of which is shown) are provided. These extend within thesupport 24 and air from the apertures 20 flows therethrough to provide alow rate of flow of air along the bore in the lining 24a.

We claim:

1. An igniter for igniting an air/fuel mixture in a combustion chamberand comprising a sleeve member, a support within the sleeve member, atarget mounted upon said support, an annular heating element supportextending into the sleeve member and defining an annular clearancetherewith, an orifice through which liquid fuel can be directed underpressure onto said target, said target being shaped so as to atomize thefuel and direct the fuel radially relative to the jet. means for causingair to flow through said clearance to produce an annular airstream intowhich the atomized fuel is directed, a heating element mounted at theend of said heating element support adjacent the target, said heatingelement when energized igniting the air/fuel mixture produced by thetarget to produce a flame which extends from the sleeve member and whichcan be used to ignite an air/fuel mixture contained in the combustionchamber, a first series of apertures formed in the sleeve member andthrough which air enters said annular clearance, and means adjacent thetarget for stabilizing the flame produced by the burning of the air/fuelmixture produced by the target.

2. An igniter as claimed in claim 4 in which the means for stabilizingthe flame comprises a second series of apertures formed in the sleevemember and through which air can enter the interior ofthe sleeve memberto produce an air stream adjacent the target.

3. An igniter as claimed in claim 1 in which the means for body part isof stepped form, the narrower portion ofthe bore accommodating saidsleeve member and said support. and the wider portion of the boreaccommodating mounting flanges for the sleeve member and support, apressure pad acting to retain the flanges within th wider portion of thebore, and a stem formed integrally with the pressure pad. said stembeing of hollow form and defining a fuel inlet at its end remote fromthe pad, the pressure pad being retained relative to the body part by anut engaged within the wider end thereof.

6. An igniter as claimed in claim 5 in which the orifice is formed in anorifice plate mounted within said stem.

7. An igniter as claimed in claim 5 in which the end of the ,body partremote from the fuel inlet defines a restricted outlet

